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Regime Shift in a Large River Fish Community: Body Size Structure and Trophic Change

Regime Shift in a Large River Fish Community: Body Size Structure and Trophic Change. Mark Pyron Center of Aquatic Biology and Fisheries Environmental Science Kyle Broadway, Brent Murry Institute for Great Lakes Research, Central Michigan University. Wabash River.

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Regime Shift in a Large River Fish Community: Body Size Structure and Trophic Change

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  1. Regime Shift in a Large River Fish Community: Body Size Structure and Trophic Change Mark Pyron Center of Aquatic Biology and Fisheries Environmental Science Kyle Broadway, Brent Murry Institute for Great Lakes Research, Central Michigan University

  2. Wabash River • 2nd largest trib of Ohio River • 85,000 km2 watershed • 764 km long

  3. Collections James Gammon 1974-98 Mark Pyron 2000-8 28 sites 230 km

  4. Jim Gammon began project 1974-98 500-m sites Boat electrofishing

  5. Sampling Protocol: • Electrofish 500 m • Collect all fishes • Measure, release

  6. Examine organisms by size Convert size-abundance matrix into size bins Regress abundances against size bins

  7. Examine organisms by size Convert size-abundance matrix into size bins Regress abundances against size bins Steeper with exploitation Steep regression = inefficient ecological transfer

  8. Wabash River size spectra analysis

  9. Trophic Groups 1974-2008

  10. Next • Isotope analyses: 13C and 15N ratios Museum archives 1974-2008 Planktivore = gizzard shad Omnivore = spotfin shiner Piscivore = spotted bass

  11. Summary • Switch in functional group dominance • Omnivores + planktivores to benthivores • Large disturbance? Change in trophic base?

  12. Funding: Eli Lilly and Company Duke Energy Ball State University Indiana Water Resources Research Center Wabash River Enhancement Corporation Collaborators: Tom Lauer, BSU Jim Gammon, Depauw U Reuben Goforth, Purdue U Many BSU students

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